46 THE CEmOIDEA CAMERATA OE NOETH AMEEICA. 



that the peripheral canals of Cupressocrinus, which consist variously of three^ 

 four, or five separate passages, correspond to the peripheral vessels of Penta- 

 crinus, Rhizocrinus, and other recent Crinoids. He directed attention to the 

 fact that there is among different individuals of the same species considerable 

 variation in the isolation of these vessels. In some species, in which the 

 canals appear to be continuous, there is but one large tri- or tetra-partite 

 perforation at the base of the calyx and throughout the stem, which he 

 thinks enclosed the four, five, or six separate vessels of other specimens. 

 This may be so, although we cannot quite understand how the three or four 

 peripheral canals, where they exist, can be extensions of a quinquelocular 

 organ. 



The variation in the size of the axial canal among Palseozoic Crinoids is 

 most remarkable. In Platycrimis the canal is sometimes no larger than the 

 point of a needle ; while in Barycrimis^ Crotalocrimis, EnaUocriniis, Megistocriniis, 

 PeriecJiocrimis, etc., it is often from one half to even three fourths the width 

 of the joints, and is either round or pentangular. In some of them the walls 

 within appear as if built up of thin laminse with spaces between, sometimes 

 pectinated and variously sculptured, producing a great multiplication of 

 exposed surfaces. In Barycrinus, with a quinque-partite stem, and a sharply 

 stellate canal, of which the projecting angles are directed radially toward 

 the suture lines, the trigonal inward extensions of the canal are pierced 

 by one or more rather large pores, which pass through the body of the 

 plates, so as to enter the outer faces of the stem, as shown on Plate I. 

 Figs. 6 and 8 a, h. Five other series of pores follow the longitudinal suture 

 lines, and these also communicate with the central canal. 



In the Crotalocrinidse and Periechocrinites, in which the central cavity is 

 proportionally still larger than in Bari/criniis, the inner structure appears to 

 have been less complex ; but its extreme size in both groups, compared with 

 that of other Crinoids, and especially with recent ones, seems to imply that it 

 was not a mere axial canal, but performed additional functions. 



We have in our collection the root of a large BarycrimiB (Plate I. 

 Fig. 7), which must have been attached to a smooth, solid substance, for 

 the lower surface of the root is perfectly flat. In this root only two of the 

 five primary branches were developed, and these are but partly preserved, 

 but enough is seen to show that they had been placed on a level with the 

 truncated lower face of the main trunk. The development of the other 

 three cirri seems to have been checked by contact with the bottom, but their 



